We appreciate the advocacy!
Remember, DEVONthink is not DEVONthink To Go and macOS is not iOS/iPadOS. Your experience on each platform is not necessarily going to be the same, especially with the different underlying filesystems.
That being said, iaWriter on mobile supports the file provider mechanism so you can open a Markdown document in a DEVONthink To Go database via the Share sheet or within iaWriter’s Library > From Other Apps.
Development would have to assess the feasibility of such changes. However, I do see how a bit of air would be good in dense text passages…
But again, remember iaWriter (like Ulysses, Typora, etc.) is a bespoke Markdown app. That’s its one trick, it’s raison d’être. So obviously it will have functions and features specific to writing. 